1. Field of the Invention
The present invention relates to a driving technique for a lighting apparatus with a light emitting diode (LED), and more particularly, to a driving circuit for a light emitting diode lighting apparatus, which is capable of illuminating an LED during the entire sections within each cycle of a pulsating current voltage, using a charging element such as a capacitor, when the LED is driven through the full-wave rectified pulsating current voltage.
2. Description of the Related Art
With the development of semiconductor technology, the efficiency of an LED has been significantly improved. Since the LED has a longer lifespan and smaller energy consumption than an existing lighting apparatus such as an incandescent lamp or fluorescent lamp, the LED is economical and environmentally-friendly. Due to such advantages, the LED is widely used as a traffic light or back light of a flat display device (for example, LCD).
In general, when the LED is used as a lighting apparatus, a plurality of LED modules each including a plurality of LEDs mounted therein are arranged in a specific manner, and then installed on the ceiling or wall surface. Each of the LED modules includes an AC/DC converter in consideration of the property of the LED which is driven by a direct current at a predetermined voltage. The above-described AC/DC converter includes a trans-coil for lowering an AC voltage. Since the trans-coil occupies a considerably large area in the LED module, a product to which the trans-coil is applied is inevitably increased in size.
In order to solve such a problem, a power supply unit referred to as a switching mode power supply (SMPS) has been conventionally used. According to the recent technology, however, the LED lighting apparatus is driven in such a manner that a plurality of LEDs are connected in series to lower a voltage for power, without using the SMPS.
The LED lighting apparatus rectifies an input AC power through a full-wave rectifier such as a bridge diode and directly illuminates an LED through a pulsating-current power. For reference, when the input AC power has a frequency of 60 Hz, the full-wave rectified pulsating current has a frequency of 120 Hz.
FIG. 1 illustrates a driving pattern of a conventional LED lighting apparatus. Referring to FIG. 1, a predetermined pattern of current is continuously supplied during a central section T2 where the voltage is equal to or more than a predetermined value in each cycle of a full-wave rectified pulsating current, thereby illuminating a corresponding LED. However, since no current is supplied during outer sections T1 and T3 where the voltage is equal to or less than the predetermined value, the corresponding LED is turned off.
In the conventional LED apparatus, when an LED is driven through the full-wave rectified pulsating voltage, the predetermined pattern of current is continuously supplied during the central section within each cycle of the pulsating-current power such that the corresponding LED is continuously illuminated. However, since no current is supplied in the outer sections, the LED is turned off. Since the operation of turning on/off the LED is performed at a very short cycle, the operation is not easily recognized with human eyes of users. However, when the human eyes are exposed to the operation for a long time, the operation may jangle the users' nerve, and thus the users may easily feel fatigue.